The invention relates to a method and an arrangement for adjusting the scanning frequency and/or scanning phase of an analog/digital converter of an image reproducing device. This image reproducing device has a digitally controlled display for displaying an image of a predefined number of lines and a predefined number of pixels per line. Therein, the image reproducing device receives digital image data from the analog/digital converter. The analog/digital converter generates the digital image data by scanning an analog video signal, which is applied to the image reproducing device, using a scanning signal of the scanning frequency and the scanning phase. Therein, the digital image data are buffered in an image memory.
To reproduce an image on the screen of a monitor tube, the video signal must be in analog form. As a result, in particular in personal computers, analog video signals must be generated if the respective images are to be reproduced on a monitor tube. The increasingly common flat screens, however, such as LC, OLED or plasma displays, which have fixed pixels that form a matrix, require a digital signal for their control. As a result, a video signal that is present in analog form must be converted into a digital signal so as to display an image on a flat screen.
The conversion of the analog signal into a digital signal regularly takes place in an analog/digital converter, in which the analog video signal is scanned using a scanning signal of a specific scanning frequency and scanning phase. It is important for the quality of the representation of an analog video signal on a flat screen, that the phase and the frequency of the scanning signal are optimally adjusted.
Due to the many different forms of analog video signals, it is almost impossible to preset the optimal frequency and phase of the scanning signal. Therefore, the adjustment of the optimal frequency and phase must take place when the image is reproduced. The result of the adjustment, however, strongly depends on the content of the image to be reproduced on the flat screen.
Conventional methods for automatically adjusting the scanning frequency do not ensure that the adjustment is performed with suitable images.